Mahmood was at the NoW for two decades, which meant that his ‘strike rate’would have to be 13 a year.

There comes a moment when an experienced investigative reporter senses something is not right – and this was one of those moments.

It just didn’t seem possible that Mahmood’s journalism could lead to an average conviction rate of one a month. Some of his strings took months to bring to a successful conclusion – and many came to nothing.

In the 1970s Rebecca was a Wales-based magazine celebrated for a hard-hitting section called the Corruption Supplement.

I edited the title but, unlike Mahmood, I could never claim that my work led to any convictions. It is true to say that about a dozen local politicians and businessmen who were named in the Corruption Supplement were later jailed.

I felt Mahmood must be gilding the lily. The investigation that followed took me and researcher Chris Nichols several weeks, going through every article Mahmood had written and every claim that he and the paper made about his strike rate.

What we found was fascinating. For the first four years of his career, there were no reports of any convictions in the NoW. He was just one of the team.

This changed when Phil Hall became editor in 1995 – he soon made Mahmood Investigations Editor and the following year the paper claimed ‘the total of villains successfully prosecuted in our pages after being exposed by Mazher’had risen ‘to a staggering EIGHTY in four years”. We could only find 18.

The ‘puffing’ of Mazher Mahmood’s successes continued relentlessly throughout the reigns of Rebekah Brooks and Andy Coulson. By the time Coulson stepped down, Mahmood’s tally apparently stood at 145 whereas our running total stood at just 62.

The apparent exaggeration continued when Colin Mylar took over as editor in 2007 – even though Clive Goodman and Mulcaire had been jailed for phone-hacking and you would have expected the paper to be ultra-vigilant.

It will be interesting to see what Lord Leveson makes of Mahmood’s admission last week that solicitors Linklaters have been able to find evidence for 94 people who were successfully prosecuted as a result of Mahmood’s journalism.

Mahmood claims that he gave Linklaters details of all the prosecutions he could recall: ‘this list exceeded 253 prosecutions [the figure he initially gave Leveson], as I believed the number included in my first statement to be a conservative estimate.”

Since he admits to keeping only a ‘broad running check’of his prosecutions, how could he come up with such a list? We’ll be asking the Leveson Inquiry team to ask him to produce that list as well as a copy of the Linklaters report.

In the meantime, Rebecca Television’s second investigation into other aspects of Mahmood’s journalism is under way.